Donaldson R F Focal Length & Crop Factor Calculator
Choose a sensor and a lens to see the crop factor, the full-frame equivalent focal length and the field of view. Everything is calculated in your browser.
The lens itself does not change: a 35 mm lens is still 35 mm. The smaller sensor simply records a narrower part of the image, so the view matches a longer lens on a full-frame camera.
I want a particular view
The same lens on other sensors
| Sensor (mm) | Crop | Equivalent | Horizontal view |
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How crop factor is calculated
The crop factor compares a sensor with the 36 × 24 mm full-frame (35 mm film) frame. Both are compared by their diagonals: crop factor = 43.27 mm ÷ sensor diagonal, where 43.27 mm is the diagonal of a full-frame sensor (√(36² + 24²)). The diagonal of a sensor is √(width² + height²). Multiply the real focal length by the crop factor to get the full-frame equivalent. The angle of view is 2 × arctan(size ÷ (2 × focal length)), worked out for the width, height and diagonal of the sensor for a lens focused at infinity; real lenses, focus breathing and distortion change it slightly.
Only the field of view is matched by the equivalent focal length. The lens's aperture, its exposure and its own optics stay the same; depth of field and image noise also depend on sensor size and are not calculated here. Sensor sizes differ slightly between models of the same format (the three APS-C examples above are not identical) and other sources may round crop factors, so use the exact dimensions in your camera's specification when accuracy matters.
Adapters and flange distance. Some lenses can be fitted to other camera bodies with an adapter. Whether that works depends on the flange distance (the gap between the lens mount and the sensor) of each system, on the lens's image circle, and on electronic contacts for autofocus and aperture. This tool does not tell you whether a lens and camera are compatible, so check the camera maker's, lens maker's and adapter maker's lists. An adapter that contains glass elements can also change the effective focal length and maximum aperture. Related tools: EXIF Viewer (see the focal length stored in a photo) and Aspect Ratio Calculator.
Source / Last verified (sensor sizes from the makers' own documents, all checked on 26 September 2026): Full frame 36.0 × 24.0 mm — Canon EOS R6 Mark II specifications, cam.start.canon/en/C012/manual/html/UG-10_Reference_0100.html. APS-C Canon 22.3 × 14.8 mm — EOS R7, cam.start.canon/en/C005/manual/html/UG-10_Reference_0100.html. APS-C Nikon DX 23.5 × 15.7 mm — Z 50, onlinemanual.nikonimglib.com/z50/en/90_technical_notes_08.html. APS-C Sony 23.3 × 15.5 mm — α6700, helpguide.sony.net/ilc/2320/v1/en/contents/221h_specifications_ilc2320.html. Micro Four Thirds 17.3 × 13.0 mm — Panasonic LUMIX G9 II, help.na.panasonic.com/answers/specifications-sheet-for-lumix-g-series-dc-g9m2/. 1-inch type 13.2 × 8.8 mm — Sony RX100 VII, helpguide.sony.net/dsc/1920/v1/en/contents/TP0002392811.html. Medium format 43.8 × 32.9 mm — Fujifilm GFX100 II, fujifilm-x.com/en-gb/products/cameras/gfx100-ii/specifications/. The crop-factor formula and the angle-of-view formula are standard geometry.